The present invention relates generally to exhaust systems and more particularly, but not exclusively, to the reduction of undesirable adsorbed substances that accumulate in an emission control system for an internal combustion engine.
Reported consequences of excessive hydrocarbon (HC) and H2O adsorption in emission control systems for internal combustion engines include significant temperature spikes and tailpipe emission of a conspicuous white vapor with a noticeable odor under certain conditions—especially after the engine idles for an extended period of time. These conditions may potentially lead to system damage or failure, which can result in service costs or warranty claims.
As a result of these hazards, damage/degradation of oxidation catalytic devices and associated soot filters has been reported. The low exhaust temperature and low space velocity (high residence time) of exhaust, which is typical for idle operations, favors HC absorption onto the surface of oxidation catalysts. Thus, for extended idle, HC accumulation may become substantial. Also H2O adsorption can become substantial under the same or similar conditions, which is particularly threatening when the system is subject to freezing temperatures while the system is nonoperational. As a consequence, a need exists for further contributions in this area of technology.